ASTM C1421-18

1.1 These test methods cover the fracture toughness, K_Ic, determination of advanced ceramics at ambient temperature. The methods determine K_Ipb (precracked beam test specimen), K_Isc (surface crack in flexure), and K_Ivb (chevron-notched beam test specimen). The fracture toughness values are determined using beam test specimens with a sharp crack. The crack is either a straight-through crack formed via bridge flexure (pb), or a semi-elliptical surface crack formed via Knoop indentation (sc), or it is formed and propagated in a chevron notch (vb), as shown in Fig. 1.